Various anti-dandruff compositions are commercially available or otherwise known in the shampoo art. These compositions typically comprise detersive surfactants and particulate, crystalline anti-microbial agents dispersed and suspended throughout the composition. Anti-microbial agents used for this purpose include sulfur, selenium sulfide and polyvalent metal salts of pyridinethione. During the shampooing process, these anti-microbial agents deposit on the scalp to provide anti-dandruff activity. Soluble anti-dandruff agents, such as ketoconazole, are also known in the art.
Nevertheless, consumers desire an anti-dandruff shampoo which provides surperior anti-dandruff efficacy.
Polyvalent metal salts of pyrithione (also known as 1-hydroxy-2-pyridinethione; 2-pyridinethiol-1-oxide; 2-pyridinethione; 2-mercaptopyridine-N-oxide; pyridinethione; and pyridinethione-N-oxide) are known to be effective biocidial agents and are widely used as fungicides and bacteriocides in paints and metalworking fluids. Polyvalent metal salts of pyrithione are also used as fungicides and bacteriocides in personal care compositions such as foot powders and anti-dandruff shampoos. The polyvalent metal salts of pyrithione are only sparingly soluble in water and include magnesium pyrithione, barium pyrithione, bismuth pyrithione, strontium pyrithione, copper pyrithione, zinc pyrithione, cadmium pyrithione, and zirconium pyrithione.
Zinc and copper pyrithione are especially useful as anti-microbial agents in personal care compositions. Zinc pyrithione is known as an anti-dandruff component in shampoos. Synthesis of polyvalent pyrithione salts is described in U.S. Pat. No. 2,809,971 to Berstein, et al. Other patents disclosing similar compounds and processes for making them include U.S. Pat. Nos. 2,786,847; 3,589,999; 3,590,035; and 3,773,770.
While pyrithione biocides have proven useful for a wide range of applications, the utility of these compounds is limited to the control of select species and strains of fungi and bacteria. Further, while higher concentrations of pyrithione salts have been observed to control the growth of a wider range of organisms, the useful amount of polyvalent metal salts of pyrithione that can be added to a commercial product is limited by efficacy and economic considerations, and environmental concerns. In personal care compositions, such as shampoos, the amounts of pyrithione salts that may be added is further limited by toxicological concerns.
Generally, the use of anti-microbial agents in anti-dandruff shampoos is also known in the art. However, although polyvalent metal salts of pyrithiones have been disclosed as anti-microbial and/or anti-dandruff agents, the overall efficacy has remained relatively low. Therefore, consumers desire a shampoo which provides superior anti-dandruff efficacy versus currently marketed products. Such a superior efficacy can be difficult to achieve.
For example, it was previously believed that anti-dandruff efficacy could be achieved by “solubilizing” a zinc pyrithione complex in a strong chelating agent. One such approach, disclosed in European Patent Application No. 077,630 to Dixon was to “solubilize” zinc pyrithione in a strong chelating agent in the presence of divalent copper cations. However, the “solubilization” process disclosed in the '630 application actually results in the break down of the chemical structure of the zinc pyrithione complex. The resulting composition contains a complex of the chelating agent/zinc in solution with free pyrithione ions. The free pyrithione ions are soluble in the composition. The '630 application discloses that this approach results in a clear product that is physically stable and provides anti-dandruff benefits.
Unfortunately, the downside risk to this approach is that excessive amounts of the soluble free pyrithione ions are known to be toxic to humans and the use of such a composition would fall outside of the current Federal Drug Administration monograph for zinc pyrithione, making the composition commercially unacceptable for personal care products.
Metal ions, such as copper salts are also taught in the art to provide efficacy in anti-microbial applications. Copper compounds, such as copper sulfate and cuprous oxide have been used widely as fungicides, antifoulants, and algaecides in a large range of applications including paints, swimming pool water, and wood products. Similarly, inorganic salts of zinc such as zinc chloride, zinc sulfate, and zinc oxide have been employed as bacteriostatic and/or fungistatic compounds in a large variety of products including paints, coatings, and antiseptics. However, copper salts and zinc salts do not possess as high a level of biocidal efficacy as might be desired for many anti-dandruff and skin care applications.
It has now surprisingly been found, in accordance with the present invention, that anti-dandruff efficacy can be dramatically increased in topical compositions by the use of polyvalent metal salts of pyrithione, such as zinc pyrithione, in combination with a metal ion source such as copper and zinc salts. It is therefore an object of the present invention to provide an anti-dandruff topical composition with improved efficacy. The improved efficacy also allows for the reduction of the levels of metal pyrithiones in anti-microbial compositions, thereby facilitating the production of safer products containing anti-microbial actives.
It is an object of the present invention to provide topical skin and/or hair compositions which provide superior anti-dandruff efficacy. It is also an object of the present invention to provide a method for cleansing the hair and/or skin. It is also an object of the present invention to provide a method for treating athlete's foot. These, and other objects, will become readily apparent from the detailed description below.